The present invention is directed to a process for controlling the infeed of a tool at the start of operation of a machine tool which operates in a continuous gear shaping process.
U.S. Pat. No. 4,195,446 discloses a gear cutting machine which operates in a continuous gear shaping process. In this machine a gear processing grinder is controlled by positive movement and operated according to the screw rolling process in which a rotating tool is controlled in its movement prior to engagement with the preprocessed toothing of a workpiece gear rotating at a predetermined rate in relation to the tool. The improvement is characterized by a sensor which may be moved between the tool and the workpiece during the running of the tool or workpiece prior to the engagement of the tool and the workpiece. U.S. Pat. No. 4,195,446 deals primarily with the alignment of the rotating tool with respect to the workpiece that is also automatically rotating at working speed. After alignment, the tool is fed in radially until it engages with the workpiece. This movement should occur as rapidly as possible in order to keep the cycle time short. In this process it is difficult to estimate the amount of movement allowable for this initial rapid infeed.
A process and an apparatus for controlling the rapid infeed of the grinding wheel of a round and flat grinding machine is disclosed in Swiss Pat. No. 585,609. This apparatus is equipped with a microphone which is responsive to ultrasonic beams. The microphone transmits the vibrations, which occur when the grinding wheel encounters the work piece, in the form of a signal to the control, which stops the rapid infeed of the grinding wheel, and switches said grinding wheel to a continuous working feed or to an incremental infeed. The use of this apparatus for gear cutting in a continuous gear shaping machine is associated with a great disadvantage since it does not consider the error given for running true that occurs when semi-machining the tooth space. If during infeed of the gear shaping tool (grinding worm, hobbing cutter, milling worm, etc.), the latter were by accident to encounter the workpiece (gear, etc.) in the lowest point of the gear's non-circularity, the layer of material to be lifted off would increase greatly in the next half of the workpiece's revolution, corresponding to the size of the deviation from the true run of the gear and eventually exceed the permissible size. This could result in frictional heat and damage to the tool.